Changelog
Changes to the public sending API and its operating limits.
October 2026: send API and web 0.40.0 allowances
The send API supports single and batch email from verified, hosted domains, organization-scoped live and test keys, outbound message activity, message details and events, and suppression dump and deletion.
Supported sending endpoints use Postmark’s format. Open and click options are accepted but ignored; webhooks, templates, other message streams and inbound processing are not available.
Web 0.40.0 adds per-plan monthly API email allowances and a daily cap of one tenth of the monthly allowance. Usage counts non-suppressed recipients at queue time in UTC calendar windows. Test sends and mailbox mail do not count.
Organization admins can see usage and request more from Developers > Sending, and receive notices at 80% and 100% of monthly usage. Limit refusals use ErrorCode 405.
See Limits and allowances for the current figures and Errors for recovery steps.